Thermodynamic Modelling of Ore-Forming Mechanism of the Changkeng Gold-Silver Deposits in Guangdong Province

The Changkeng gold-silver deposits consist of a sediment-hosted, disseminated gold deposit and a replacement-type silver deposit. The mineralizations of gold and silver are zoned and closely related to the silicification of carbonate and clastic rocks, so that siliceous ores dominate in the deposit. The mineralizing temperature ranges mainly from 300 to 170℃, and K+, Na+, Ca2+, Mg2+, and Cl- are the major ions in the ore-forming fluid. Calculations of distribution of metal complexes show that gold is mainly transported by hydrosulphide complexes, but chloride complexes of silver, iron, lead, and zinc, which are transformed into hydroxyl and hydrosulphide complexes under neutral to weak-alkaline circumstances in the late stage, predominate in the ore-forming solutions. Water-rock interaction is confirmed to be the effective mechanism for the formation of silver ores by computer modelling of reaction of hydrothermal solution with carbonate rocks. The solubility analyses demonstrate that the precipitation     

晋北后所金矿床地质特征及矿床成因

后所金矿是产在五台群变质岩中的金矿床，有含金黄铁矿石英脉型和蚀变岩型两种矿化类型本文论述了后所金矿的地质特征，矿物组成，微量元素，稳定同位素地球化学和矿物馀本学特征，探讨了金矿的物质来源和金矿成因，指出了金矿的演化和最后定位于燕山中晚期。     

关于金矿成矿物质来源的初步探讨

近年来“矿源层”这一概念已被广大地质学家所接受，他们认为矿床中的金是从围岩中萃取的，本文认为矿床中的金来源于岩浆残余热液。在地壳深部，当丰度值高的基性岩或其他岩石，在深熔作用下产生花岗质岩浆时，同时带出许多金，当岩浆侵入到上部地壳冷凝结晶时，其中的大部金进入残余热液，最后富集成矿。     

青海德令哈巴音郭勒河断裂带的新活动特征

在青海德令哈巴音郭勒河北侧山前冲洪积扇上新发现了一条长约60km的逆断裂带,属于本区NNW-NWW向的柴达木盆地北缘活动断裂系内的一条次级挤压构造。断裂在地貌上表现为明显的挤压逆冲断层陡坎,晚更新世晚期以来的平均垂直滑动速率为0.41±0.27mm/a。探槽剖面确定了三次古地震事件,其年代分别为距今约32.7±1.45ka、15.54±1.32ka和3.2±0.33ka。     

赣南中侏罗世流纹岩地球化学及成因研究：上地壳成因的的微量元素和Pb-Nd-Sr同位素地球化学制约

江西南部龙南-寻邬地区余田群菖蒲组的流纹岩形成于中侏罗世(164．8．1Ma～174．9Ma)，为双峰式火山岩组合的酸性端元，属弱过铝质(ACNK平均为1．04)钙碱性系列(σ平均为1．90)。稀土元素含量高(平均为278．9μg/g)，轻稀土富集(IMH平均为7．94)，Eu亏损中等(δEu平均为0．41)。微量元素以富集Rb，Ba，Th，U，Zr，Y，Pb，而亏损Sr，Nb为特征。Pb，Nd，Sr同位素组成为：(^206Pb/^204Pb)t=17．89～18．58，(^207Pb/^204Pb)t=15．58～15．70，(^208Pb/^204Pb)t=37．94～38．82；εNd(t)=-7．44～-11．9；ISr=0．71126～0．71228。对赣南流纹岩微量元素采用蛛网图和模糊聚类分析方法进行对比研究的结果及Pb-Nd-Sr同位素相关特征为其上地壳成因提供了地球化学佐证。赣南流纹岩是由进入上地壳内高位岩浆房的石英拉斑玄武岩浆的底侵作用直接使上地壳部分熔融形成的产物。     

基于GIS的孔隙水文地质层三维空间离散方法

针对自然界中孔隙水文地质层空间分布的不连续性与厚度分布的不均匀性,研究基于GIS的孔隙水文地质层三维空间离散实现的技术路线,提出基于GIS的孔隙水文地质层不规则六面体元的三维空间离散方法.该法不仅能最大限度地保证不规则六面体元中水文地质层类型的一元性,而且可充分利用GIS的空间分析与数据的自动提取功能,快速提取各个计算结点上空间位置坐标与各类计算参数,大大缩短水文地质模型空间离散与相关数据文件组织所需的时间,提高地下水三维有限差分数值模拟的时效性,具有较高的实用价值.     

U–Pb ages of Neoarchean granitoids from the Black Hills, South Dakota, USA: implications for crustal evolution in the Archean Wyoming province

Zircons in basement rocks from the eastern Wyoming province (Black Hills, South Dakota, USA) have been analyzed by ion microprobe (SHRIMP) in order to determine precise ages of Archean tectonomagmatic events. In the northern Black Hills (NBH) near Nemo, Phanerozoic and Proterozoic (meta)sedimentary rocks are nonconformably underlain by Archean biotite–feldspar gneiss (BFG) and Little Elk gneissic granite (LEG), both of which intrude older schists. The Archean granitoid gneisses exhibit a pervasive NW–SE-trending fabric, whereas an earlier NE–SW-trending fabric occurs sporadically only in the BFG, which is intruded by the somewhat younger LEG. Zircon crystals obtained from the LEG and BFG exhibit double terminations, oscillatory zoning, and Th/U ratios of 0.6±0.3—thereby confirming a magmatic origin for both lithologies. In situ analysis of the most U–Pb concordant domains yields equivalent ²⁰⁷Pb/²⁰⁶Pb ages (upper intercept, U–Pb concordia) of 2559±6 and 2563±6 Ma (both ±2σ) for the LEG and BFG, respectively, which constrains a late Neoarchean age for sequential pulses of magmatism in the NBH. Unzoned (in BSE) patches of 2560 Ma zircon commonly truncate coeval zonation in the same crystals with no change in Th/U ratio, suggesting that deuteric, fluid-assisted recrystallization accompanied post-magmatic cooling. A xenocrystic core of magmatic zircon observed in one LEG zircon yields a concordant age of 2894±6 Ma (±2σ). This xenocryst represents the oldest crustal material reported thus far in the Black Hills. Whether this older zircon originated as unmelted residue of 2900 Ma crust that potentially underlies the Black Hills or as detritus derived from 2900 Ma crustal sources in the Wyoming province cannot be discerned. In the southern Black Hills (SBH), the peraluminous granite at Bear Mountain (BMG) of previously unknown age intrudes biotite–plagioclase schist. Zircon crystals from the BMG are highly metamict and altered, but locally preserve small domains suitable for in situ analysis. A U–Pb concordia upper intercept age of 2596±11 Ma (±2σ) obtained for zircon confirms both the late Neoarchean magmatic age of the BMG and a minimum age for the schist it intrudes. Taken together, these data indicate that the Neoarchean basement granitoids were emplaced at 2590–2600 Ma (SBH) and 2560 Ma (NBH), most likely in response to subduction associated with plate convergence (final assembly of supercontinent Kenorland?). In contrast, thin rims present on some LEG–BFG zircons exhibit strong U–Pb discordance, high common Pb, and low Th/U ratios—suggesting growth or modification under hydrothermal conditions, as previously suggested for similar zircons from SE Wyoming. The LEG–BFG zircon rims yield a nominal upper intercept date of 1940–2180 Ma, which may represent a composite of multiple rifting events known to have affected the Nemo area between 2480 and 1960 Ma. Together, these observations confirm the existence of a Paleoproterozoic rift margin along the easternmost Wyoming craton. Moreover, the 2480–1960 Ma time frame inferred for rifting in the Black Hills (Nemo area) corresponds closely to a 2450–2100 Ma time frame previously inferred for the fragmentation of supercontinent Kenorland.     

Application of Remote Sensing in Flood Management with Special Reference to Monsoon Asia: A Review

The conventional means to record hydrological parameters of aflood often fail to record an extreme event. Remote sensingtechnology along with geographic information system (GIS)has become the key tool for flood monitoring in recent years.Development in this field has evolved from optical to radarremote sensing, which has provided all weather capabilitycompared to the optical sensors for the purpose of flood mapping.The central focus in this field revolves around delineation of floodzones and preparation of flood hazard maps for the vulnerable areas.In this exercise flood depth is considered crucial for flood hazardmapping and a digital elevation model (DEM) is considered to bethe most effective means to estimate flood depth from remotelysensed or hydrological data. In a flat terrain accuracy of floodestimation depends primarily on the resolution of the DEM. Riverflooding in the developing countries of monsoon Asia is very acutebecause of their heavy dependence on agriculture but any floodestimation or hazard mapping attempt in this region is handicappedby poor availability of high resolution DEMs. This paper presents areview of application of remote sensing and GIS in flood managementwith particular focus on the developing countries of Asia.     

亚、欧两大洲自然地理环境结构的整体性和差异性教学初探

地理环境的结构，是指地理环境各组成要素之间和各组成部分之间相互关系性质的组合，它包括既有联系、又有区别的两个方面，即地理环境结构的整体性和差异性。笔者在亚、欧两洲自然地理数年的教学实践中，从自然环境结构的整体性和差异性特征入手，得出分析、综合、概括归纳和对比研究等方法是学习世界区域地理的主要方法。     

SAN技术在基础地理信息数据库系统建设中的应用

分析了基础地理信息数据库建设中对存储备份系统的需求和当前存储系统的组成及特点 ,提出了存储局域网在基础地理信息数据库系统建设中的应用方案 ,并介绍了其在陕西省基础地理信息数据库系统建设中的实现情况